Vehicles having electric motors as their driving sources are known, such as hybrid vehicles, electric vehicles, and fuel cell vehicles. Each of such vehicle is provided with a battery for storing electric power to be supplied to the electric motor. Some of the vehicles are configured to be capable of charging the battery with electric power supplied from a power supply external to the vehicle. Hereinafter, a vehicle capable of charging the battery with electric power supplied from a power supply external to the vehicle is also referred to as a plug-in vehicle. Electric power is supplied to a battery mounted on a plug-in vehicle via a charging cable or the like connected to the plug-in vehicle.
A well known technology relating to PLC (Power Line Communication) makes it possible to utilize a charging cable as a communication path. Generally, PLC is capable of sending and receiving data faster than wireless communication. Therefore, a fast transmission of data for use in, for example, a car navigation system for a plug-in vehicle can be achieved by PLC utilizing a charging cable, instead of wireless communication utilizing a mobile phone or the like.
However, PLC is not always more suitable than wireless communication. Thus, a technology for making a switch between PLC and wireless communication depending on the state of communication has been proposed.
Japanese Patent Laying-Open No. 2003-229790 (Patent Literature 1) discloses a communication system that makes a selective switch between a wireless system, which performs communication with the other party of the communication via a wireless line, and a wire system, which performs communication with the other party of the communication via a power line supplying electric power to a communication terminal, to perform communication. The communication system detects the communication quality of each of the wireless and wire systems and makes a system switch to a system with better communication quality.